Channel-type induction furnace

ABSTRACT

Channel type induction furnace provided with a nozzle for blowing gas into the channel at a position which prevents formation of oxides and the like due to eddy currents.

United States Patent 1191 F olgero et al.

1451 Feb. 12, 1974 [54] CHANNEL-TYPE INDUCTION FURNACE 3,618,917 11/1971 Fredrikson et a1 13/29 X 2,805,271 9/1957 Lan l3/29 [751 inventors Karfihlgefm Vasteras; 3,192,303 6/1965 0155111 13/29 x Hellsmg, Fmspong, both of Sweden [73] Assignee: Allmanna Svenska Elektriska Akfiebolaget, vastel'as, Sweden Primary Examiner-Roy N. Envall, Jr. Attorney, Agent, or Firm-Kenyon & Kenyon Reilly 22 Fl d. A 24, 1972 l 1 I e ug Carr & Chapm [21] Appl. No.2 283,425

[30] Foreign Application Priority Data Sept. 9, 1971 Sweden 11412/71 [57] ABSTRACT [52] US. Cl. 13/2 51 1111. Q1 F27d 11/06, HOSb 5/14 Channel mducm furnace Pmvlded a [58] Field of Search 13/29 2 lie for Owing gas the channel a Position which prevents formation of oxides and the like due to [56] References Cited eddy currents- UNITED STATES PATENTS 3,591,698 7/1971 Howard et al. 13/29 7 Claims, 3 Drawing Figures I f \l 1 CHANNEL-TYPE INDUCTION FURNACE BACKGROUND OF THE INVENTION The present invention relates to a channel-type induction furnace having at least one inductor, comprising at least two side channels leading from the furnace hearth and a bottom channel connecting the parts of the side channels facing away from the hearth and provided with members for blowing gas into the channel.

Such a furnace is described in our Swedish Pat. No. 328,967, both in single and double-channel design. In this furnace construction porous nozzles are applied in the bottom channel, directed towards the side channels, for blowing in an inert gas and possibly a gas re acting with parts of the content of the furnace.

One drawback with this type of furnace is that deposits of oxides and the like occur due to the eddy currents in the channel where two gas flows meet (at A in FIG. 3) and furthermore the number of porous plugs and corresponding recesses required in this case is rather large.

SUMMARY OF THE INVENTION The present invention relates to another solution of the problems solved by the object of said patent and lacks the drawbacks mentioned. The invention is characterised in that at least one nozzle is arranged below each coil at the part of the channel located furthest away from the hearth, to blow gas into the channel, for example inert gas and possibly a gas which reacts with part of the contents of the furnace. Thus one set of nozzles and corresponding recesses can be dispensed with in relation to the object of the above patent, while at the same time satisfactory temperature equalization is obtained in the channel, less deposits on the walls of the channel (Note: at (A) in FIG. 3) and it is possible to give the channel a suitable shape from the point of view of efficiency and power factor, for example circular channel shape, concentric with the coil(s).

THE DRAWINGS The furnace is further exemplified in the accompanying drawings in which FIG. 1 shows a single channel,

PREFERRED EMBODIMENT FIG. 1 shows a single phase furnace having a primary coil 11, usually for 50-60 Hz, and a channel 12 of ceramic stamping compound 13 or lining compound of conventional type (it may also be casting compound) arranged around the coil 11 and preferably concentric with this, both ends of this channel opening out into a furnace hearth 14. The number of such inductor units may be one or more. At the bottom of the channel, in the case shown furthest away from the hearth 14, a porous, gas-permeable plug 15 is arranged for the introduction of gas into the channel, for example an inert gas and possible a gas (16, 17) such as chlorine which reacts with part of the contents of the furnace so that a cleansing effect is obtained on melts of the type containing aluminium, magnesium or similar metals which in previously known types of furnaces cause oxide deposits on the walls of the channels and may even clog the channels.

As is known, the circular channel shape gives high coscb and efficiency in relation to rectangular or square channel shape (in section) and the positioning of the plug, a single plug, makes it possible to construct a circular length of channel (in a plane across the coil). However, it is also possible to construct the channel with more or less straight side channels and a bottom channel connecting these.

In the case shown the plug 15 is placed symmetrically and it is possible to acquire a flow which is suitable for temperature equalization and to prevent deposits. At each blowing-in section the number of part-nozzles may be one or more, for example one for inert gas and one for active gas. However, two or more such partnozzles require only one recess and may together be deemed to comprise one nozzle.

The object of blowing in gas is therefore partly to prevent local overheating and partly, if an active gas is used, to allow the gas to react with parts of the furnace contents. The flow of the melt in the channel can also reduce or eliminate deposits on the channels walls. The number of turbulences in the flow pattern will be small, which is also an advantage both from the deposit and the temperature equalization point of view. The prevention of over-temperatures also means that the furnace can be run on full power for a longer period.

FIG. 2 shows two such nozzles 18, 19, or sets of nozzles, in a furnace of twin-coil type, single or two phase. In this case also, one set less may be used than the number of channels running between hearth 20 and bottom channel (two side and one central channel 21, 22, 23.). Although unidirectional bath movement in the classical sense is not obtained, a flow is obtained which facilitates temperature equalization and impedes deposits, the latter being further assisted if an active gas is also used.

The furnace construction can be varied in many ways within the scope of the following claims.

What is claimed is:

1. In a channel-type induction furnace having at least one inductor and in which the channel comprises two side channels leading from the furnace hearth and a bottom channel connecting said two side channels, means to blow gas through said channels so as to avoid a build up of deposits on the channel wall comprising:

a. a gas discharge device located essentially at the midpoint of said bottom channel on the opposite side of the inductor coil from the hearth; and

b. means to supply a gas to said gas discharge device.

2. The invention according to claim 1 wherein said gas discharge device comprises a single nozzle and said means to supply supplies as inert gas.

3. The invention according to claim 1 wherein said gas discharge device comprises at least two nozzles and said means to supply comprises means to supply an inert gas to one nozzle and means to supply a gas which will react with the furnace contents to the other nozzle.

4. The invention according to claim 1 wherein each of said side channels and said bottom channel comprises an annular section essentially concentric with the induction coil, thereby forming a rounded annular channel and wherein said gas discharge device is located at a point equidistant from the openings of said annular channel into the hearth.

5. In a channel-type induction furnace having at least one inductor and in which the channel comprises first, second and third spaced side channels extending away from the furnace hearth, the second channel being between the first and third channels, and a bottom channel connecting said side channels, means to blow gas through said channels so as to avoid a build up of deposits on the channel walls comprising:

a. a first gas discharge device located in the bottom channel essentially at the midpoint between the first and second channels;

b. a second gas discharge device located in the bottom channel essentially at the midpoint of said second and third channels; and c. means to supply gas to said first and second gas discharge devices. 6. The invention according to claim 4 wherein each 5 of said gas discharge devices comprises a nozzle and said means to supply comprises a source of inert gas.

7. The invention according to claim 4 wherein each of said first and second discharge devices comprises at least two nozzles and said means to supply gas comprises means to supply an inert gas to one nozzle and means to supply a gas which reacts with the furnace contents to the other nozzle in each device. 

1. In a channel-type induction furnace having at least one inductor and in which the channel comprises two side channels leading from the furnace hearth and a bottom channel connecting said two side channels, means to blow gas through said channels so as to avoid a build up of deposits on the channel wall comprising: a. a gas discharge device located essentially at the midpoint of said bottom channel on the opposite side of the inductor coil from the hearth; and b. means to supply a gas to said gas discharge device.
 2. The invention according to claim 1 wherein said gas discharge device comprises a single nozzle and said means to supply supplies as inert gas.
 3. The invention according to claim 1 wherein said gas discharge device comprises at least two nozzles and said means to supply comprises means to supply an inert gas to one nozzle and means to supply a gas which will react with the furnace contents to the other nozzle.
 4. The invention according to claim 1 wherein each of said side channels and said bottom channel comprises an annular section essentially concentric with the induction coil, thereby forming a rounded annular channel and wherein said gas discharge device is located at a point equidistant from the openings of said annular channel into the hearth.
 5. In a channel-type induction furnace having at least one inductor and in which the channel comprises first, second and third spaced side channels extending away from the furnace hearth, the second channel being between the first and third channels, and a bottom channel connecting said side channels, means to blow gas through said channels so as to avoid a build up of deposits on the channel walls comprising: a. a first gas discharge device located in the bottom channel essentially at the midpoint between the first and second channels; b. a second gas discharge device located in the bottom channel essentially at the midpoint of said second and third channels; and c. means to supply gas to said first and second gas discharge devices.
 6. The invention According to claim 4 wherein each of said gas discharge devices comprises a nozzle and said means to supply comprises a source of inert gas.
 7. The invention according to claim 4 wherein each of said first and second discharge devices comprises at least two nozzles and said means to supply gas comprises means to supply an inert gas to one nozzle and means to supply a gas which reacts with the furnace contents to the other nozzle in each device. 